Vienna Codex depicts the ritual use of mushrooms by the Mixtec gods, showing Piltzintecuhtli and 7 other gods holding mushrooms in their hands. These were most likely psilocybin-containing mushrooms. (The Wondrous Mushroom)

The use of hallucinogenic mushrooms and peyote are driven underground as use of "non-alcohol" intoxicants is forbidden by Europeans in Mexico. Catholic priests punish the use of entheogens by native people.

Spanish priest Bernardino de Sahagún writes in his Florentine Codex about the use of peyote and hallucinogenic teonanacatl mushrooms by the Aztecs. He estimates peyote has been in use since at least 300 B.C.
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Physician W. Heberden writes to the Gentlemen's Magazine of a family eating mushrooms, which rendered them "all much disordered". The man "was unable to shut his eyes and was so giddy he could hardly stand; the woman felt the same symptoms in a more violent degree; and the child, who had but just tasted them, had convulsive agitations in its arms."
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First psychedelic mushroom experience/ingestion documented in a scholarly journal takes place in London. Dr. Everard Brande attends a family whose members, upon eating wild mushrooms, were seized with visions and laughter. The mushrooms were examined and determined to be Agaricus glutinosus, later reclassified as Psilocybe semilanceata (Liberty Caps).
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Amateur mycologist R. Gordon Wasson visits Oaxaca Mexico and sits in on a mushroom velada. In 1954 returns to Huatla with Alan Richardson a photographer, to 'complete' his research of mind altering mushrooms. He returns again in 1955 with Richardson for the fateful velada with Maria Sabina.

Weil and Russin write a scathing critique of Leary and Alpert's work in the Harvard Crimson: Far from exercising the caution that characterizes the published statements of most scientists, Leary and Alpert, in their papers and speeches, have been given to making the kind of pronouncement about their work that one associates with quacks.
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"The shoddiness of their work as scientists is the result less of incompetence than of a conscious rejection of scientific ways of looking at things. Leary and Alpert fancy themselves 'prophets' of a psychic revolution designed to free Western man from the limitations of consciousness as we know it."

The Comprehensive Drug Abuse Prevention and Control Act is passed. Part II of this is the Controlled Substance Act (CSA) which defines a scheduling system for drugs. It places most of the known hallucinogens (LSD, psilocybin, psilocin, mescaline, peyote, cannabis, & MDA) in Schedule I. It places coca, cocaine and injectable methamphetamine in Schedule II. Other amphetamines and stimulants, including non-injectable methamphetamine are placed in Schedule III.

The British government announces that they have "re-interpreted" the law and are now declaring the sale of fresh psilocybin mushrooms a "preparation" and therefore illegal. Some shops close, but other remain open and some are shut down by police. Eventually charges are dropped and some shops remain open.

Survey results published in Neurology show that both psilocybin-containing mushrooms and LSD may reduce severity and frequency of cluster headaches.
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Erowid participated in this research by working with Clusterbusters.com to publish and solicit responses to a survey about the use of psilocybin to treat cluster headaches. Some of the participants in the later Sewell survey were found through Erowid's earlier online survey.